The present invention relates generally to an eyeglass manufacturing method using a layer with a variable index of refraction. More specifically, the present invention pertains to patient-specific spectacle lenses manufactured with an variable index aberrator in order to more accurately correct lower order aberrations and additionally correct higher order aberrations. The present invention also provides a means for correcting vision problems caused by retinal dysfunction.
Present manufacturing techniques for eyeglass lenses are capable of producing lenses that correct only the lower order (sphere and cylinder) aberrations. Customarily, lens blanks are available in discrete steps of refractive power of 0.25 diopters. In most cases, these steps are too large to create optimum vision for a patient""s eye.
Current manufacturing techniques do not effectively treat vision problems resulting from retinal dysfunction. For example, in macular degeneration, patients suffer from vision loss in selective areas of the fundus, typically close to the center of vision. Laser treatment of the affected areas further destroys retinal tissue, causing blindness at the treated areas. Clinical studies have shown that the human eye and brain are capable of switching to other areas of the retina to substitute the damaged area with an undamaged area. In other words, damaged areas in the retina are essentially bypassed by the brain. Ultimately, vision loss will occur as a portion of an image falls on the damaged retina. Consequently, there is a need to manufacture an eyepiece such that the image may be xe2x80x9cwarpedxe2x80x9d around the dysfunctional tissue in order to allow the entire image to focus on the remaining healthy tissue.
In light of the aforementioned problems, the need for an optical element which generates a unique wavefront phase profile becomes apparent. Traditional manufacturing methods create such profiles through grinding and polishing. Such a method of manufacture is very costly due to the amount of time and expertise required.
The present invention utilizes the technology developed by the wavefront aberrator in which a layer of variable index material, such as curable epoxy, can be sandwiched between two plane or curved glass or plastic plates. This sandwich is then exposed to the curing radiation (i.e., UV light) that is modulated spatially or temporally in order to create spatially resolved variations of refractive indices. This will allow the manufacturing of a lens that is capable of introducing or compensating for low and high order aberrations.
In the simplest form, two lens blanks are sandwiched together with a layer of epoxy such that the lenses used in conjunction approximately correct the patient""s refractive spherical and cylindrical correction to within 0.25 diopters. Subsequently, the epoxy aberrator would be exposed to curing radiation in a pre-programmed way in order to fine-tune the refractive properties of the spectacle lens to the exact spherical and cylindrical prescription of the patient""s eye.
Another application of the present invention is to manufacture multi-focal or progressive addition lenses constructed with a layer of variable index material sandwiched in between the two lens blanks. The drawback of progressive addition lenses today is that, like regular spectacle lenses, a true customization for a patient""s eye cannot be achieved due to the current manufacturing techniques. Using the two lenses and epoxy, a customized progressive addition lens or reading lens can be manufactured by appropriately programming the curing of the epoxy aberrator.
The present invention provides a method to manufacture lenses that give patients xe2x80x9csupervision.xe2x80x9d In order to achieve supervision, higher order aberrations of the patient""s eye need to be corrected. Since these higher order aberrations, unlike the spherical and cylindrical refractive error, are highly asymmetrical, centering of the eye""s optical axis with the zone of higher order correction (xe2x80x9csupervision zonexe2x80x9d) is important. To minimize this effect, one could devise a spectacle lens that incorporates a supervision zone only along the central optical axis, allowing the patient to achieve supervision for one or more discrete gazing angles. The remainder of the lens would then be cured to correct only the lower order aberrations. An optional transition zone could be created between the supervision zone and the normal vision zone allowing for a gradual reduction of higher order aberrations. Again, all of this would be achieved by spatially resolved programming of the epoxy aberrator""s curing.
In order to cover a larger field of view with supervision, a multitude of supervision xe2x80x9cislandsxe2x80x9d might be created. The supervision islands then are connected by transition zones that are programmed to gradually change the higher order aberrations in order to create smooth transitions.
In bifocal lenses, refractive power in discrete steps of 1 diopter is added in the lower area of the lens to aid the spectacle wearer in near distance viewing, i.e. reading. For cosmetic reasons, the visible dividing line between the distance viewing area and the reading area is disliked by many presbyobic patients. With the event of the progressive addition lens, the sharp dividing line between the distance area and the reading area has been eliminated by introducing a continuous varifocal corridor of vision with a refractive power slowly changing from the distance viewing prescription to the reading prescription.
However, due to manufacturing limitations several disadvantages exist with the progressive addition lens. First, vision through areas outside the corridor is noticeably distorted, making the progressive addition lens unsuitable for many patients. Second, while the patient""s individual prescription is applied to the distance viewing area, the added refractive power for the reading area is only offered in discrete steps of 1 diopter. Third, the distance between the centers of the distance viewing and reading viewing areas is fixed by the lens design and cannot be changed to accommodate for an individual""s preference or application. Furthermore, the corridor design is fixed for any particular brand of lens and cannot be changed according to the patient""s actual viewing preferences or spectacle frame selected.
Therefore, when prescribing a progressive addition lens, the eye care professional has to choose from an assortment of designs and manufacturers the lens which matches the requirements of the patient most closely. The present invention allows to manufacture a lens that is entirely customized and optimized to the patient""s individual requirements.
Lastly, the present invention may be used to xe2x80x9cwarpxe2x80x9d the retinal image so that damaged portions of the retina will be bypassed by the image. In order to do this, the visual field of the patient needs to be mapped with a perimeter or micro-perimeter. From this map of healthy retina, spectacle lenses could be manufactured using the epoxy aberrator.